yann@251: Hi,
yann@251: 
yann@251: The attached patch makes sure that we create smaller object code for
yann@251: simple switch statements. We just make sure to flatten the switch
yann@251: statement into an if-else chain, basically.
yann@251: 
yann@251: This fixes a size-regression as compared to gcc-3.4, as can be seen
yann@251: below.
yann@251: 
yann@251: 2007-04-15  Bernhard Fischer  <..>
yann@251: 
yann@251: 	* stmt.c (expand_case): Do not create a complex binary tree when
yann@251: 	optimizing for size but rather use the simple ordered list.
yann@251: 	(emit_case_nodes): do not emit jumps to the default_label when
yann@251: 	optimizing for size.
yann@251: 
yann@251: Not regtested so far.
yann@251: Comments?
yann@251: 
yann@251: Attached is the test switch.c mentioned below.
yann@251: 
yann@251: $ for i in 2.95 3.3 3.4 4.0 4.1 4.2.orig-HEAD 4.3.orig-HEAD 4.3-HEAD;do
yann@251: gcc-$i  -DCHAIN -Os -o switch-CHAIN-$i.o -c switch.c ;done
yann@251: $ for i in 2.95 3.3 3.4 4.0 4.1 4.2.orig-HEAD 4.3.orig-HEAD 4.3-HEAD;do
yann@251: gcc-$i  -UCHAIN -Os -o switch-$i.o -c switch.c ;done
yann@251: 
yann@251: $ size switch-*.o
yann@251:    text	   data	    bss	    dec	    hex	filename
yann@251:     169	      0	      0	    169	     a9	switch-2.95.o
yann@251:     115	      0	      0	    115	     73	switch-3.3.o
yann@251:     103	      0	      0	    103	     67	switch-3.4.o
yann@251:     124	      0	      0	    124	     7c	switch-4.0.o
yann@251:     124	      0	      0	    124	     7c	switch-4.1.o
yann@251:     124	      0	      0	    124	     7c	switch-4.2.orig-HEAD.o
yann@251:      95	      0	      0	     95	     5f	switch-4.3-HEAD.o
yann@251:     124	      0	      0	    124	     7c	switch-4.3.orig-HEAD.o
yann@251:     166	      0	      0	    166	     a6	switch-CHAIN-2.95.o
yann@251:     111	      0	      0	    111	     6f	switch-CHAIN-3.3.o
yann@251:      95	      0	      0	     95	     5f	switch-CHAIN-3.4.o
yann@251:      95	      0	      0	     95	     5f	switch-CHAIN-4.0.o
yann@251:      95	      0	      0	     95	     5f	switch-CHAIN-4.1.o
yann@251:      95	      0	      0	     95	     5f	switch-CHAIN-4.2.orig-HEAD.o
yann@251:      95	      0	      0	     95	     5f	switch-CHAIN-4.3-HEAD.o
yann@251:      95	      0	      0	     95	     5f	switch-CHAIN-4.3.orig-HEAD.o
yann@251: 
yann@251: 
yann@251: Content-Type: text/x-diff; charset=us-ascii
yann@251: Content-Disposition: attachment; filename="gcc-4.3.gcc-flatten-switch-stmt.00.diff"
yann@251: 
yann@251: Index: gcc-4.2.0/gcc/stmt.c
yann@251: ===================================================================
yann@251: --- gcc-4.2.0.orig/gcc/stmt.c	(revision 123843)
yann@251: +++ gcc-4.2.0/gcc/stmt.c	(working copy)
yann@251: @@ -2517,7 +2517,11 @@ expand_case (tree exp)
yann@251:  	  use_cost_table
yann@251:  	    = (TREE_CODE (orig_type) != ENUMERAL_TYPE
yann@251:  	       && estimate_case_costs (case_list));
yann@251: -	  balance_case_nodes (&case_list, NULL);
yann@251: +	  /* When optimizing for size, we want a straight list to avoid
yann@251: +	     jumps as much as possible. This basically creates an if-else
yann@251: +	     chain.  */
yann@251: +	  if (!optimize_size)
yann@251: +	    balance_case_nodes (&case_list, NULL);
yann@251:  	  emit_case_nodes (index, case_list, default_label, index_type);
yann@251:  	  emit_jump (default_label);
yann@251:  	}
yann@251: @@ -3075,6 +3079,7 @@ emit_case_nodes (rtx index, case_node_pt
yann@251:  	    {
yann@251:  	      if (!node_has_low_bound (node, index_type))
yann@251:  		{
yann@251: +		  if (!optimize_size) /* don't jl to the .default_label. */
yann@251:  		  emit_cmp_and_jump_insns (index,
yann@251:  					   convert_modes
yann@251:  					   (mode, imode,
yann@251: 
yann@251: 
yann@251: Content-Type: text/x-csrc; charset=us-ascii
yann@251: Content-Disposition: attachment; filename="switch.c"
yann@251: 
yann@251: int
yann@251: commutative_tree_code (int code)
yann@251: {
yann@251: #define CASE(val, ret) case val:/* __asm__("# val="#val ",ret="#ret);*/ return ret;
yann@251: #ifndef CHAIN
yann@251:   switch (code)
yann@251:     {
yann@251: # if 1
yann@251:   CASE(1,3)
yann@251:   CASE(3,2)
yann@251:   CASE(5,8)
yann@251:   CASE(7,1)
yann@251:   CASE(33,4)
yann@251:   CASE(44,9)
yann@251:   CASE(55,10)
yann@251:   CASE(66,-1)
yann@251:   CASE(77,99)
yann@251:   CASE(666,0)
yann@251: # else
yann@251:     case 1:
yann@251:       return 3;
yann@251:     case 3:
yann@251:       return 2;
yann@251:     case 5:
yann@251:       return 8;
yann@251:     case 7:
yann@251:       return 1;
yann@251:     case 33:
yann@251:       return 4;
yann@251:     case 44:
yann@251:       return 9;
yann@251:     case 55:
yann@251:       return 10;
yann@251:     case 66:
yann@251:       return -1;
yann@251:     case 77:
yann@251:       return 99;
yann@251:     case 666:
yann@251:       return 0;
yann@251: # endif
yann@251:     default:
yann@251:       break;
yann@251:     }
yann@251:   return 4711;
yann@251: 
yann@251: #else
yann@251:    if (code == 1)
yann@251: 	return 3;
yann@251:   else if (code == 3)
yann@251: 	return 2;
yann@251:   else if (code == 5)
yann@251: 	return 8;
yann@251:   else if (code == 7)
yann@251: 	return 1;
yann@251:   else if (code == 33)
yann@251: 	return 4;
yann@251:   else if (code == 44)
yann@251: 	return 9;
yann@251:   else if (code == 55)
yann@251: 	return 10;
yann@251:   else if (code == 66)
yann@251: 	return -1;
yann@251:   else if (code == 77)
yann@251: 	return 99;
yann@251:   else if (code == 666)
yann@251: 	return 0;
yann@251:   else
yann@251: 	return 4711;
yann@251: #endif
yann@251: }
yann@251: 
yann@251: 
yann@251: --AhhlLboLdkugWU4S--
yann@251: